The present invention relates to an improvement of installed objects such as inset lights installed inside the concrete pavement, for example, runway, taxiway, apron and road in an airport, and more particularly to inset lights and other objects installed inside the prestressed concrete pavement.
A conventional inset light (or marker light) has a structure as shown in FIG.6. This inset light 30 is installed inside, for example, the runway in an airport, and is roughly composed of a cylindrical base 32 installed inside a prestressed concrete pavement (hereinafter called PC pavement) 31, and a lamp body 34 mounted on the base 32 through (using) a lamp body holding member 33 called adjusting ring. The inset light 30 can be easily installed inside the PC pavement 31 by placing concrete after arranging it among with the conduit pipe, PC steel materials, the parts of PC pavement and others at specified position on the existing pavement surface.
In the above-mentioned inset light 30, however, since the outer circumference of the base 32 is a flat cylindrical body, the coupling force (engagement) between the outer circumference of the base 32 and the PC pavement 31 is not strong by nature. When a heavy load of aircraft or the like is applied on the top of the lamp body 34, since the resistance between the cylindrical outer circumference of the base 32 and the PC pavement 31 is small, the load is concentrated in the lower part of the base 32. As the load exceeding the strength of the PC pavement 31 at the lower side of the base 32 is applied from the bottom of the base 32, the concrete portion of the lower side of the base may be broken, and the lighting fixture is likely to sink.
At this time, in the PC pavement 31 beneath the base 32, simultaneously with the load pressure acting directly from the lower side of the base 32, a normal stress for direction of bottom (shearing force) acts from the edge portion at the lower end of the base 32. Therefore, when a heavy load of aircraft or the like repeatedly acts on the inset light 30, the portion of the PC pavement 31 supporting the base 32 may be cracked in a short period and be brittle, thereby sinking the inset light 30.
A first object of the invention is to present an inset light capable of preventing concentration of the load beneath the base of the inset light if a heavy load of aircraft or the like is applied, by oppressing the outer circumference of the base 32 by utilizing effectively the prestress applied to the PC pavement 31, and raising the coupling force with the PC pavement 31.
As indicated by arrow S0, the prestress from the PC pavement 31 acts to oppress the outer circumference of the base 32, but the prestress applied to oppress the outer circumference of the base 32 of which rigidity is larger than that of the PC pavement 31 is canceled by the replusive force of the outer circumference of the base (binding force=canceling force in the opposite direction). Accordingly, the bonding force with the PC pavement is lowered, and the base holding force by the PC pavement drops. Moreover, since the replusive force of the base 32 has a component in a direction of canceling the prestress of the PC pavement 31, shortage of prestress of the PC pavement 31 occurs in the lower side portion of the base 32, that is, in the portion of supporting the load applied to the base 32. Since the PC pavement 31 maintains the concrete strength by a predetermined prestress, if the prestress is insufficient, the strength declines. However, the outer circumference of the base 32 which is a cylindrical body with a bottom is made of a metal plate 32a, and is deformed somewhat in the plate thickness direction due to stress from the direction intersecting with the plate surface, the reduction of stress force is smaller than in the lower edge of the base.
By contrast, the lower edge of the base corresponds to the outer peripheral edge of the bottom plate 32b, and is the most rigid portion that is hardly deformed, and it overcomes the prestress S0 from the above-mentioned direction, and cancels the prestress from the PC pavement. Thus, by the replusive force of the lower edge of the base 32, the prestress acting on the PC pavement positioned beneath the bottom of the base is decreased, and the concrete strength in the area declines. In this state, when a heavy load is applied to the top of the lighting fixture from aircraft or the like, the PC pavement portion positioned beneath the base is cracked by the bending stress, and finally the inset light 30 sinks and troubles are likely to occur.
It is a second object of the invention to present an inset light capable of preventing lowering of strength in the concrete portion positioned beneath the base, while effectively enhancing the bonding force between the base and the PC pavement, by minimizing the region of cancellation of prestress due to constraint of the prestress on the outer circumference by the base for composing the inset light installed inside the PC pavement, so that the prestress may act more effectively on the entire base.
To achieve the objects, a first embodiment of the invention relates to an inset light comprising a cylindrical base installed inside a prestressed concrete (PC) pavement, and a lamp body held on the top of the base for emitting light out to the pavement surface, in which protruded deformations are formed on the outer circumference of the base in order to receive the load applied on the lamp body from above at the PC pavement around the base.
In a second embodiment of the invention, the protruded deformations have a function of dispersing the stress generated downward from the lower edge of the base by the load applied on the lamp body from above.
In a third embodiment of the invention, the protruded deformations are disposed at specific pitches along the axial direction of the base.
In a fourth embodiment of the invention, the longitudinal sectional shape of the protruded deformations is formed in a sine wave shape.
In a fifth embodiment of the invention, the longitudinal sectional shape of the protruded deformations is formed in a trapezoidal shape.
In a sixth embodiment of the invention, the protruded deformations are composed by fusing wires at specific pitches on the outer circumference of the base.
In a seventh embodiment of the invention, a shock absorber is provided at the lower outer edge of the base.
In an eighth embodiment of the invention, the prestressed concrete pavement is replaced by a structure, such as reinforced concrete pavement, having a thermal expansion and capable of burying and supporting an object in the concrete or the like in a state of constraint around the buried object.
In a ninth embodiment of the invention, the structure of the inset light in any one of the other embodiments is applied to a buried object other than the inset light.